#include <iostream>

class ExpressCompany
{
public:
    virtual void sendPackage() {}
};

class SF : public ExpressCompany
{
public:
    void sendPackage() override
    {
        std::cout << "SF 为您发送快递，主打一个快" << std::endl;
    }
};

class JDL : public ExpressCompany
{
public:
    void sendPackage() override
    {
        std::cout << "JDL 为您改善快递，最快可当日送达" << std::endl;
    }
};


void sendPackage(ExpressCompany& express) 
{
    express.sendPackage();
}

